Fuel Injection Control System for an Automotive Engine
The present invention relates to a system for controlling the fuel injection of an automotive engine in dependence on a throttle opening degree and engine speed.
In a known fuel injection system, a basic fuel injection pulse width Tp is calculated in dependence on throttle opening degree .theta. and engine speed N. The basic pulse width Tp are stored in a table shown in FIG. 4 and are derived for controlling the fuel injection during the operation of the engine. At a transient state of the operation of the engine, the basic fuel injection pulse width Tp is corrected in dependence on various factors such as engine speed, pressure in an intake passage, coolant temperature and vehicle speed, so as to provide an optimum air fuel ratio (see for example, Japanese Patent Laid Open 55-32913).
However, in the system, the basic injection pulse width table must have a larger number of lattices in accordance with opening degree .theta. and engine speed N. The reason is that, as indicated in FIG. 4, the basic injection pulse width Tp varies inconstantly. Especially in a low engine speed and small opening degree region, the pulse width changes at a large rate. Thus, a memory having a large capacity must be provided for the table.
Moreover, if the variables .theta. and N are out of the range of the table in an extreme condition, for example extremely low engine speed which is slightly higher than a speed where the engine may stall, it is impossible to obtain an optimum basic injection pulse width.